The continuous processing of nitroglycerin generally produces a waste-water stream which must be treated so that it can meet rigid pollution standards. In order to determine the effectiveness of the pollution abatement equipment, there is a need for a continuous monitoring device for measuring and monitoring the concentration of nitroglycerin in waste water before and after the pollution treatment equipment.
Prior art polargraphic devices generally apply a linear voltage ramp to a dropping mercury electrode of an electrochemical cell. These devices in some cases measure the increase in current due to an electro-oxidizable or reducible species and display this current on a sensing and/or recording type instrument. Other prior art polargraphic devices take the derivative of the resulting signal, which is generally noisy, and display the signal oscillographically. Derivative circuitry is not only noisy, but is complex, expensive and not amenable to use in a continuous monitor, although it is entirely acceptable for laboratory type instrumentation used to spot check a sample solution. Other prior art polargraphic devices ramp the applied voltage to the electrochemical cell and while pulsing the ramp voltage measure the change in cell current before and after the pulse. Some prior art polargraphs use a dropping mercury type electrode in order to provide a continually new, fresh, mercury surface with which to work. The dropping mercury type electrode is very difficult to use in a continuous monitor because of the variation in time in the dropping of the mercury from capillaries and the need for synchronization of current sensing circuitry. Use in the prior art of a stationary mercury electrode precludes renewal of electrode surface. In the aforementioned prior art polargraphic device, the stationary mercury electrode surface frequently becomes fouled cathode various species and byproducts of the electro-oxidation-reduction start as the applied voltage is varied over the potential ranges of interest and often becomes unreliable and insensitive as a continuous monitor of waste water.